US4043372A - Pneumatic tire for off-road vehicles - Google Patents

Pneumatic tire for off-road vehicles Download PDF

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Publication number
US4043372A
US4043372A US05/664,227 US66422776A US4043372A US 4043372 A US4043372 A US 4043372A US 66422776 A US66422776 A US 66422776A US 4043372 A US4043372 A US 4043372A
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Prior art keywords
tire
plies
breaker
carcass
tread
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Inventor
Isao Miyoshi
Masaru Abe
Toshiro Tezuka
Toshio Yoshimoto
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Bridgestone Corp
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Bridgestone Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C15/00—Tyre beads, e.g. ply turn-up or overlap
    • B60C15/04—Bead cores
    • B60C15/05—Bead cores multiple, i.e. with two or more cores in each bead
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/02—Carcasses
    • B60C9/04—Carcasses the reinforcing cords of each carcass ply arranged in a substantially parallel relationship
    • B60C9/06—Carcasses the reinforcing cords of each carcass ply arranged in a substantially parallel relationship the cords extend diagonally from bead to bead and run in opposite directions in each successive carcass ply, i.e. bias angle ply
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C2200/00—Tyres specially adapted for particular applications
    • B60C2200/14—Tyres specially adapted for particular applications for off-road use

Definitions

  • This invention relates to a pneumatic tire for off-road vehicles, which is highly durable under heavy load conditions.
  • the pneumatic tire for off-road vehicles is classified by JIS D6401 into the following two kinds of tires, i.e.
  • the pneumatic tire for off-road vehicles is classified into: (1) a tire for industrial vehicles such as a forklift truck, tractor for industrial vehicles; (2) various kinds of low speed trailers, straddle carrier, small type shovel loader and other relatively low speed trucks and (3) into a tire for construction vehicles such as scrapers for excavation, loading, carrying, scraping and other operations; a heavy dump truck, motor grades, tiredozer; tractor shovel; shovel loader, tire roller and the like.
  • a tire for construction vehicles is classified into the first kind of tires such as (1) a tire for motor trucks for carrying soil and used for travel on irregular ground such as sandy ground, muddy ground and the like inherent to the works of dam, aqueduct, road, residential land and the like; (2) a tire for motor trucks used for travel on hard and irregular grounds such as dam building yards, river improving yards, stone pits, mining yards and the like, (3) a tire for a lumber carrying vehicle used for travel on irregular ground where stubs are scattered as in a forest and the like and (4) tires for vehicles used under substantially the same conditions as mentioned above.
  • a tire for motor trucks for carrying soil and used for travel on irregular ground such as sandy ground, muddy ground and the like inherent to the works of dam, aqueduct, road, residential land and the like
  • a tire for motor trucks used for travel on hard and irregular grounds such as dam building yards, river improving yards, stone pits, mining yards and the like
  • a tire for a lumber carrying vehicle used for travel on irregular ground where stubs are scattered as
  • tires such as (1) a tire for a tractor shovel, shovel loader, low speed crane used for loading soil, sand and ore and excavation in plants, public works, harbor works and the like, (2) a tire for tiredozers and tires used under substantially the same conditions as mentioned above.
  • nylon breaker tire comprising a carcass body composed of rubberized ply layers superimposed one upon the other and each containing relatively durable nylon cords embedded therein and assembled into a bias construction in which the cords of approximately one-half of the carcass ply layers are extended in an opposite direction to the cords associated with the remaining carcass ply layers with respect to the equatorial line of the tire, and a breaker superimposed about the crown portion of the carcass body and carcass body and composed of at least one rubberized layer each containing the relatively durable nylon cords embedded therein and assembled into the bias construction.
  • the above-mentioned nylon breaker tire has disadvantages when the tire is used for travel on off-road where obstructions such as rocks, pieces of broken metal, glass and wood, stubs are scattered thereon, particularly under such condition that the load subjected to one tire is large, cut failure is liable to occur at the tread rubber surface, which often leads to fatal tire failure thus rendering the tire useless.
  • the tread rubber surface is subjected to a number of relatively small cuts which are not so fatal as to render the use of the tire impossible. These cuts, however, induce frequent occurrence of "cut abrasion" that causes the rubber layer to drop pieces.
  • An object of the invention is to provide a pneumatic tire for off-road vehicles, which can obviate all of the disadvantages which have been encountered with the above mentioned prior art techniques.
  • Another object of the invention is to provide a pneumatic tire for off-road vehicles, which is highly durable under heavy load conditions, has an excellent cut resistant property without cut abrasion and heat separation failure and can be used for a long time.
  • a carcass body is composed of a plurality of rubberized ply layers superimposed one upn the other and each containing organic fiber cords embedded therein and assembled into a bias construction in which the cords of approximately one-half of the carcass ply layers are extended in an opposite direction to the cords associated with the remaining carcass ply layers with respect to the equatorial line of the tire in the same manner as in the case of the prior art technique in general.
  • the cords of each of the carcass ply layers are extended in an opposite direction to the cords associated with the adjacent carcass ply layers with respect to the equatorial line of the tire.
  • the cords of each of the carcass ply layers may be locally extended in the same direction as the cords associated with the adjacent carcass ply layers with respect to the equatorial line of the tire.
  • the number of those carcass ply layers which contain the cords extended in directions opposite with each other may be different from each other.
  • substantially total ply layers are extended from the crown portion of the tire through the side portion up to the bead member where at least one portion of the total ply layers are wound about the bead cores.
  • a breaker is superimposed about the crown portion of the carcass body and composed of at least one rubberized layer each containing reinforcing elements embedded therein.
  • the breaker makes use of a reinforcing element formed of material having an excellent cut resistant property, i.e. a high tensile strength having a high modulus of elasticity such as a steel cord
  • a reinforcing element formed of material having an excellent cut resistant property i.e. a high tensile strength having a high modulus of elasticity
  • the difference between the modulus of elasticity of the breaker whose reinforcing elements are formed of the steel cord and the modulus of elasticity of the tread rubber and the carcass ply whose cords are formed of organic fiber such as nylon and the like becomes considerably large if compared with the case in which the breaker uses reinforcing elements formed of organic fiber such as nylon and the like. As a result, the separation tire failure is liable to occur.
  • the thickness of the rubber layer for surrounding the reinforcing element formed of steel cords of the breaker which is called a cushion layer, is required to be far greater than the thickness of the reinforcing element formed of organic fiber such as nylon and the like.
  • a cushion layer is required to be far greater than the thickness of the reinforcing element formed of organic fiber such as nylon and the like.
  • the total thickness inclusive of the thickness of the tread rubber layer, the thickness of the breaker layer and the thickness of the carcass ply layer of the steel breaker tire becomes far greater than the total thickness of all of the above mentioned layers of the nylon breaker tire.
  • the great total thickness of all of the above mentioned layers of the steel breaker tire significantly prevents heat radiation effect thereof which can transfer the heat generated in the tire due to the hysteresis loss during rotation of the tire under load to the outside of tire, thereby accumulating heat in the tire.
  • Heat accumulation leads to a temperature rise in the tire. This temperature rise in the tire accelerates heat fatigue which induces heat separation failure of the tire.
  • a lower limit of temperature for maintaining steel cord-to-rubber bonding by the conventional technique which does not disregard economy of the production of tire on the basis of commerce becomes considerably lower than the lower limit of temperature for maintaining organic fiber cord-to-rubber bonding by the same conventional technique.
  • heat separation failure is liable to frequently occur.
  • the heat separation failure in the steel breaker tire occurs at a time which is earlier than the time at which the heat separation occurs in the nylon breaker tire when both tires are used for travel at the same speed under the same load.
  • the breaker makes use of a reinforcing element formed of material having a high cut resistant property, which is represented by a steel wire, that is, material having a tensile strength of at least 140 Kg/mm 2 , preferably at least 170 Kg/mm 2 and at least 200 Kg/mm 2 when a maximum cut resistant property is required, such high modulus of elasticity together with the above mentioned great total thicknes required for preventing the separation failure due to the mechanical fatigue make the modulus of elasticity and bending rigidity of the tire as a whole considerably large, and as a result, so-called enveloping power for enveloping rocks and the like when the tire rides on the rocks and the like is reduced.
  • a reinforcing element formed of material having a high cut resistant property, which is represented by a steel wire, that is, material having a tensile strength of at least 140 Kg/mm 2 , preferably at least 170 Kg/mm 2 and at least 200 Kg/mm 2 when a maximum cut resistant property is required,
  • This reduction of the enveloping power serves to increase pressure subject to the tread surface of the tire when the tire rides on the rocks and the like, so that the tread surface is liable to be worn by abrasion and hence so-called cut abrasion (which causes rubber to be scraped off by cuts) is accelerated to degrade the wear resistant property of the tire, thereby shortening life of the tire due to wear.
  • the above mentioned decrease of the enveloping power corresponds to decrease of faculty of absorbing external energy of the tire as a whole, the external energy being subjected to the tire from the road surface. It is a matter of course that such decrease of the faculty of absorbing the external energy of the tire as a whole results in an increase of energy and local concentration thereof required for the tread layer, breaker layer and carcass layer for the purpose of withstanding the external force subjected to the tire.
  • the breaker having a high modulus of elasticity is obliged to withstand the above mentioned increased energy that tends to induce premature failure. This, too, results in an insufficient display of the merit of the higher cut resistance property of the breaker and induces premature separation failure from that part of the breaker which has been subjected to the premature cut failure, thereby degrading the overall durability of the tire.
  • the total thickness of the crown portion of the tire is required to be decreased.
  • the prior art bonding techniques which have been effected without disregarding the economy of the production of tire on the basis of commerce involve necessity of a sufficiently great thickness of the cushion rubber layer for the purpose of preventing the separation failure due to the mechanical fatigue.
  • the thickness of the tread rubber layer is obliged to be decreased.
  • the decrease of the thickness of the tread rubber layer results in a shortage of the wear life of the tire which is an important subsidiary to the cut resistant property of the tire and hence such shortage of the wear life of the tire could not be permitted.
  • the use of at least one breaker layer composed of a reinforcing element having a high cut resistant property and superimposed about a carcass body of a bias construction ensures no provision of means for increasing the cut resistant property of the breaker by the carcass itself, which has been required in the case of the prior art nylon breaker tire, and that the carcass body is only required to have faculty of withstanding both the internal pressure applied to the tire and the external force struck against the tire.
  • the invention therefore, is based on such recognitions that the above mentioned prior art problems arising from the prior art bonding techniques can be eliminated by decreasing the number of plies of the carcass body to the least possible extent.
  • the number of plies of the carcass body is defined on the basis of the above recognitions as follows.
  • a pneumatic tire for off-road vehicles which makes use as its breaker of a reinforcing element formed of material having a high cut resistant property such as steel or glass
  • the least possible number of those plies of a plurality of ply layers of a carcass body which are extended from a crown portion of the tire through both side portions up to both bead members and which can substantially withstand internal pressure applied to the tire and external force subjected thereto is determined on the basis of a fundamental safety factor ⁇ given by ##EQU1## and which lies within a range of a correction safety factor ⁇ which depends on the use and type of the tire and the depth of tread groove and which is given by
  • T c is a tensile strength of a cord (Kg/1 cord)
  • P is a standard internal pressure defined by JIS D6401 or an internal pressure recommended by TRA YEAR BOOK published in U.S.A. for tires with sizes not defined by JIS (Kg/cm 2 ),
  • Nn is number of cords per 5 cm of each ply (Number of cords/5 cm),
  • ⁇ n is an angle of cords in each ply inclined with respect to the equatorial line of the tire (°),
  • R m is a distance from the rotational axis of the tire to the innermost ply of the carcass body at the crown portion of the tire (cm),
  • n is number of the carcass plies which can withstand the internal pressure applied to the tire and the external force subjected thereto,
  • K 1 is a coefficient having a value in dependence with the use of the tire:
  • K 2 is a coefficient having a value in dependence with the type of tire:
  • K 3 is a coefficient having a value in dependence with the depth of treat groove:
  • K 2 and K 3 being always 1 for the tire for industrial vehicles.
  • the pneumatic tire for off-road vehicles comprising the above mentioned carcass plies whose least possible number is determined on the basis of the fundamental safety factor ⁇ and lies within the range of the correction safety factor ⁇ is capable of collectively making the rigidity, thickness, mechanical strength of the carcass optimum, and of significantly improving the cut resistant property of the tire.
  • the carcass body has the following three faculties, that is,
  • the faculty A is capable of not only reliably maintaining static internal pressure applied to the tire but also of reliably maintaining the internal pressure applied to the tire even when the tire is subjected to various kinds of dynamic external forces during running on the road surface under load and even when the carcass becomes damaged by obstructions scattered on the road surface in the case that the tire rides thereon and hence is subjected to the dynamic external force.
  • the strength of the carcass is given by strength against the internal pressure applied to the tire + surplus strength against the external force subjected to the carcass + surplus strength against cuts.
  • the safety factor ⁇ of the conventional tire carcass will now be described.
  • the safety factor of the conventional tire carcass for off-road vehicles represented by a pneumatic tire for construction vehicles is large and is 9 to 19.
  • the pneumatic tires for off-road vehicles are divided into two kinds, that is, a tire for travel at a low speed such as a tire for loaders and a tire for travel at a high speed such as a tire for dumps or scrapers.
  • the service conditions of the tire for travel at the low speed are very different from those of the tire for travel at the high speed, so that the severity subjected to the former tire is different from the severity subjected to the latter tire.
  • the safety factor of the former tire is 9 to 13 while the safety factor of the latter tire is 14 to 19 which is larger than that of the former tire.
  • the safety factor of the carcass of a tire for vehicles which is suited for travel on paved or substantially paved road, i.e. a passenger automobile, light truck, truck or bus is 8 to 9 which is smaller than that of the tire for construction vehicles.
  • the tread surface portion of the tire is frequently subjected to cut failure due to obstructions such as sharp rocks, pieces of broken metal and glass, stubs, etc. and hence the tire becomes useless.
  • the tire for off-road vehicles therefore, is obliged to increase the number of the carcass plies and increase the total thickness of the carcass for the purpose of preventing the cut failure from reaching to the inner surface of the tire and hence of alleviating the tire failure. That is, surplus strength against cut failure must be made large. As a result, the safety factor of the carcass of the tire for off-road vehicles must be made significantly large if compared with that of the tire for paved road vehicles.
  • This disadvantage can be alleviated by defining the least possible number of plies of the carcass body on the basis of the safety factor of the carcass by the above mentioned formulae according to the invention, thereby collectively optimizing the rigidity, thickness, strength, etc. of the carcass.
  • the use of the measures described ensures omission of "the surplus strength against the cut failure" from the constitutional elements of the tire for off-road vehicles and provides the important advantage that the presence of the breaker layer having an excellent cut resistant property causes the carcass to optimize the rigidity, thickness, strength, etc. thereof.
  • the cut resistant breaker layers may be divided into a plurality of sections in their widthwise direction, respectively, the sections being spaced apart from each other.
  • a rubberized layer containing organic fiber cords embedded therein may be superimposed about not only the rubberized breaker layer but also about the carcass ply for the purpose of improving the recap property of the tire.
  • the rubberized layer containing the organic fiber cords embedded therein may be superimposed about each side edge of the rubberized breaker layer.
  • the center skipped construction of the carcass body according to the invention makes it possible to obtain the above mentioned advantageous effect but also reduce deflection of that portion of the tire in its widthwise direction which is located at a position immediately below the load subjected to the load, thereby alleviating cut failure of the side portion of the tire struck by sharp rocks.
  • This is because of the fact that the thickness and hence the rigidity of the side portion of the tire according to the invention is the same as that of the prior art tire.
  • carcass plies may be skipped at their crown center portions or skipped along entire width thereof in dependence with the use and service conditions of the tire.
  • the invention is capable of applying the conventional high cut resistant breaker tire, which has been used under limited service conditions only due to the above mentioned various kinds of disadvantages thereof, to a pneumatic tire for off-road vehicles, which can be used for travel on various kinds of road surfaces, and is capable of considerably improving substantial safety factor of the tire as a whole even though the strength of the carcass body thereof is weaker than that of the nylon breaker tire.
  • the pneumatic tire for off-road vehicles according to the invention makes use of an optimum amount of material, so that it is possible to decrease the amount of material being used, thereby making the tire less expensive and hence contributing greatly to recent desires for conservation of energy and natural resources.
  • the pneumatic tire for off-road vehicles according to the invention can decrease the number of carcass plies and hence the number of bead cores from double bead cores to a single bead core and from triple bead cores to double bead cores, thereby significantly increasing yield of tires.
  • FIG. 1 is a cross sectional view of a center skipped tire for off-road vehicle according to the invention
  • FIG. 2A is a graph which illustrates the cut resistant property of the tire according to the invention compared with those of the conventional tires;
  • FIG. 2B is a cross sectional view of the tire to be tested mounted on a testing machine
  • FIG. 3 is a graph which illustrates the test result yielded from an acceleration test applied to the tire according to the invention compared with those of the conventional tires;
  • FIG. 4 is a cross sectional view of another embodiment of the tire according to the invention in which the number of carcass plies is decreased;
  • FIG. 5 is a cross sectional view of a further embodiment of the tire according to the invention which makes use of a modified arrangement of the breaker;
  • FIG. 6 is a cross-sectional view of a still further embodiment of the tire according to the invention.
  • FIG. 7 is a cross sectional view of another embodiment of the tire according to the invention in which two plies are skipped at the center portion of the tire;
  • FIG. 8 is a cross sectional view of another embodiment of the tire according to the invention which shows a modified arrangement of the breaker.
  • FIGS. 9 to 12 are sectional views of various modified embodiments of the tire according to the invention which make use of various forms of a breaker protective layer, respectively.
  • FIG. 1 a cross section of one-half of a tire, parts being shown vertical center section through the rotational axis of the tire.
  • the tire shown in FIG. 1 is of the 3rd kind of tire for construction vehicles (defined by JIS D6401), and belongs to a wide base tire having a regular tread and a size of 17.5-25 12PR, being indicated on the basis of a cotton yarn.
  • the tire shown in FIG. 1 comprises a bead member 1 composed of two sets of bead cores 1a, 1b and a carcass ply 2 composed of 8 plies each formed of a nylon cord of 1,260 denier/2 strands.
  • plies 2a of the total eight plies are wound about the bead core 1d from the inside toward the outside thereof and secured to the bead member 1.
  • Two plies 3 of the four plies 2a which are located at the outside of a center part of the tire are skipped by a width which is substantially the same as the width of two breaker layers 7a, 7b each having an excellent cut resistant property.
  • These two outside plies 3 serve as plies for reinforcing the side portion of the tire.
  • the number of plies 2a at the crown tread portion of the tire becomes two, but the four plies 2a are extended from the hump portion of the tire to the bead core 1a are wound about the bead core 1a from the inside toward the outside thereof and secured to the bead member 1.
  • Two plies 2b are extended from the center portion of the tire to the bead member 1 and wound about the bead core 1b from the inside toward the outside thereof and secured to the bead member 1.
  • two outermost plies 2c are extended from the center portion of the tire to the bead member 1 where these two outermost plies 2c are extended from the outside along the lower surface of the bead cores 1b 1a toward the inside thereof and secured at their inner ends to a toe portion 1d of the bead member 1.
  • the above mentioned construction may be called as a crown center skipped carcass ply.
  • the cords of these carcass plies are disposed in each of the plies and extended along two opposite directions symmetrically inclined at an angle of approximately 36° with respect to the equatorial line of the tire.
  • breaker layers 7a, 7b each composed of a rubberized fabric containing steel cords which constitute a reinforcing element.
  • the width of these breaker layers 7a, 7b is approximately 90% of the tread width.
  • Each of these breaker layers 7a, 7b is composed of a rubberized fabric containing stranded steel cords of 1 ⁇ 4 ⁇ 5 ⁇ 4 ⁇ 1 (a filament diameter is 0.175 mm and a cord diameter is 1.26 mm).
  • the number of the steel cords per 5 cm of the rubberized fabric is 18.
  • the safety factor ⁇ of the above mentioned carcass ply obtained by the above mentioned calculation formulae was 7.9. It is a matter of course that the above mentioned two plies 3 for reinforcing the side portion of the tire is not taken into the calculation.
  • FIG. 2A is shown a graph which illustrates an improved cut resistant property of the tire built as above described manner compared with those of the prior art tires.
  • a tire to be tested T shown in FIG. 2B is mounted on a standard rim R of 14.00 ⁇ 25 and pressurized to a standard internal pressure of 3.5 Kg/cm 2 as defined by JIS D6401
  • the tire T is mounted on Amsler's testing machine which makes use of a tapered sharp cutter 9 (FIG. 2B) whose taper angle is approximately 15°, blade width is 60 mm and blade length is 80 mm.
  • the cutter 9 is formed of SKH3 and thrusted against the center of the tire to be tested T with a speed of 50 mm/min as shown in FIG. 2B.
  • the cut resistant property of the tire to be tested T was observed with respect to a breaking load in Kg as a function of the amount of penetration of the cutter 8 into the tire T which will be described hereinafter as displacement of the cutter B.
  • a curve A shows the test result of the tire according to the present example 1
  • a curve B shows the test result of a tire comprising a carcass ply 2a shown in FIG. 1, the 4 plies 2a of which are extended from the center portion of the tire to the bead core 1a and are wound about the bead core 11a from the inside toward the outside thereof and secured to the bead member 1 and two breaker layers each containing 34 stranded nylon cords per 5 cm, each stranded nylon cord being composed of 840 denier/2 strands, and the other structure being the same as that of the example 1, and a dotted lines curve C shows the test result of a WUT tire (Wire Under Tread tire) composed of a rubberized layer containing wires each having a diameter of 0.15 mm and a length of 12 mm, a weight ratio of the wires to rubber being 10%.
  • WUT tire Wire Under Tread tire
  • This WUT layer having a thickness of 10 mm is inserted between the breaker layers and the tread rubber layer.
  • the tread rubber layer becomes thin in thickness by the thickness of the WUT layer.
  • the other structure of the WUT tire is the same as that of the tire shown by the curve B.
  • the breaking load indicating the cut resistant property of the tire of the example 1 according to the invention is two times stronger than those of the nylon breaker tire shown by the curve B and WUT tire shown by the dotted lines curve C.
  • FIG. 3 is shown a test result of the separation resistant property of the tire of the example 1 according to the invention as compared with those of the conventional tires.
  • load ⁇ speed per hour in Ton.Km/Hour is taken on ordinate and running time in hour is taken on abscissa.
  • the test is of an accelerated one effected by an indoor drum testing machine.
  • the tire was pressurized to an internal pressure of 3.5 Kg/cm 2 .
  • the load was increased from 60% to 170% in a stepwise manner as shown in FIG. 3 with the speed made constant as 11 Km/hour. In this case, 100% load corresponds to 6,135 Kg on the basis of the standard load for 17.5-25 tire as defined by JIS D6401.
  • a point A shows a separation occurrence point in the conventional steel breaker tire
  • a point B shows a separation occurrence point in the conventional nylon breaker tire
  • C shows a separation failure occurrence point in the steel breaker tire of the example 1 according to the invention having the center skipped carcass ply.
  • the conventional steel breaker tire exceeded its limit temperature at the third step of 100% load, thus resulting in the breaker separation due to overheat.
  • the tire of the example 1 according to the invention safely passed through the 3rd step and arrived at the 5th step of 150% load where the breaker layer showed separation therein.
  • This separation resistant property of the tire of the example 1 according to the invention is substantially equal to that of the conventional nylon breaker tire shown by the point B.
  • the tire of the example 1 according to the invention makes use of the steel breaker layers which are easily liable to separation occurrence therein, but has an excellent separation resistant property whic is comparable to that of the conventional nylon breaker tire.
  • FIG. 4 is shown a cross section of one-half of a tire, parts being shown vertical center section through the rotational axis of the tire.
  • the tire shown in FIG. 4 is of the third kind of tire for construction vehicles (defined by JIS D6401) and belongs to a wide base tire having a regular tread and a size of 17.5-25 12PR.
  • the thickness of the tread is the same as that of the tread of the example 1.
  • the tire shown in FIG. 4 comprises a bead member 1 composed of one bead core 1a and a carcass ply 2 composed of 6 plies each formed of a nylon cord of 1,260 denier/2 strands.
  • Two outermost plies 2b are extended from the center portion of the tire to the bead member 1 where these two outermost plies 2c are extended from the outside along the lower surface of the bead core 1a toward the inside thereof and secured at their inner ends to a toe portion 1d of the bead member 1.
  • the conventional nylon breaker tire comprises a carcass ply composed of 8 plies each formed of a nylon cord of 1,260 denier/2 strands.
  • the tire of the example 2 according to the invention comprises a carcass ply composed of 6 plies, so that it may be called as a total width skipped carcass ply.
  • the cords of these carcass plies are disposed in each of the plies and extended along two opposite directions symmetrically inclined at an angle of approximately 36° with respect to the equatorial line of the tire.
  • breaker layers 7a, 7b each composed of a rubberized fabric containing steel cords which constitute a reinforcing element.
  • the width of the breaker layer 7a is 0.90 TW (TW is a tread width) and the width of the breaker layer 7b is 0.5 TW.
  • Each of these breaker layers 7a, 7b is composed of a rubberized fabric containing stranded steel cords of 1 ⁇ 4 ⁇ 6 ⁇ 4 ⁇ 1 (a filament diameter is 0.175 mm and a cord diameter is 1.26 mm).
  • the number of the steel cords per 5 cm of the rubberized fabric is 18. These steel cords are disposed in each of the rubberized layers and extended along two opposite directions symmetrically inclined at an angle of approximately 36° with respect to the equatorial line of the tire.
  • the curve A also shows the cut resistant property of the tire of the example 2 according to the invention which is two times stronger than those of the nylon breaker tire shown by the curve B and the WUT tire shown by the dotted lines curve C.
  • a point D shows a separation failure occurrence point in the steel breaker tire of the example 2 according to the invention having the total width skipped carcass ply.
  • each of the two breaker layers 7a, 7b superimposed about the carcass plies 2 shown in FIG. 4 is composed of a rubberized fabric containing a bundle of 14 helically formed steel filaments and constituting a reinforcing element.
  • Each filament has a diameter of 0.25 mm and the bundle has a diameter of 1.17 mm.
  • the number of bundles per 100 mm of the rubberized fabric is 36.
  • the other construction is substantially the same as that of the example 2.
  • the diameter of the bundle becomes varied in accordance with the manner of assembling the steel filaments, so that is given by
  • n is the number of filaments per one bundle.
  • the width of the breaker layer 7a is 0.90 TW and the width of the breaker layer 7b is 0.5 TW as shown in FIG. 4.
  • FIG. 5 is shown another embodiment of the tire according to the invention in which the width of both the two breaker layers 7a, 7b is made 0.4 to 0.6 TW.
  • FIG. 6 is shown a cross section of one-half of the 1st kind of tire for construction vehicles (defined by DIS 6401) belonging to an ordinary tire having an extra tread, parts being shown vertical center section through the rotational axis of the tire.
  • the tire shown in FIG. 6 has a size of 24.00-49 42PR, 42PR being indicated on the basis of a cotton yarn.
  • the carcass ply is of a crown center skipped carcass ply as in the example 1shown in FIG. 1.
  • the tire shown in FIG. 6 comprises a bead member 1 composed of 3 sets of bead cores 1a, 1b, 1c and a carcass ply 2 composed of 32 plies each formed of a nylon cord of 1,260 denier/2 strands.
  • Ten plies 2a are wound about the bead core 1a from the inside toward the outside thereof and secured to the bead member 1.
  • Ten plies 2b are wound about the bead core 1b from the inside toward the outside thereof and secured to the bead member 1.
  • Ten plies 2c are wound about the bead core 1c from the inside toward the outside thereof and secured to the bead member 1. Those eight plies 3 of the plies 2c which are located at the crown center portion of the tire are skipped by a width which is substantially the same as the width of two breaker layers 7a, 7b each having an excellent cut resistant property. As a result, the number of plies 2c at the crown portion of the tire becomes 2, but the 10 plies 2c are extended from the hump portion of the tire to the bead core 1c and are wound about the bead core 1c from the inside toward the outside thereof and secured to the bead member 1.
  • two outermost plies 2d are extended from the crown center portion of the tire to the bead member 1 where these 2 outermost plies 2c are extended from the outside along the lower surface of the bead cores 1c, 1c, 1a toward the inside thereof and secured at their inner ends to a toe portion 1d of the bead member 1.
  • the above mentioned construction is of a crown center skipped carcass ply, so that the thickness of the crown portion of the tire is thinner by approximately 10 mm than the thickness of the crown portion of a tire whose carcass ply is composed of 32 plies.
  • the cords of these carcass plies are disposed in each of the plies and extended along two opposite directions symmetrically inclined at an angle of approximately 35° with respect to the equatorial line of the tire.
  • breaker layers 7a, 7b each composed of a rubberized fabric containing steel cords which constitute a reinforcing element.
  • the width of these breaker layers 7a, 7b is approximately 90% of the tread width.
  • Each of these breaker layers 7a, 7b is composed of a rubberized fabric containing standed steel cords of 1 ⁇ 4+6 ⁇ 4+1 (a filament diameter is 0.175 mm and a cord diameter is 1.26 mm). Eighteen steel cords per 5 cm of the rubberized fabric are used. These steel cords are disposed in each of the rubberized layers and extended along two opposite directions symmetrically inclined at an angle of approximately 36° with respect to the equatorial line of the tire.
  • the safety factor of the carcass ply of the tire of the example 4 according to the invention obtained by the above mentioned calculation formulae was 13.2. It is a matter of course that the above mentioned eight plies 3 for reinforcing the side portion only of the tire are not taken into the calculation of the safety factor.
  • FIG. 7 is shown a cross section of one-half of the 1st kind of tire for construction vehicles (defined by DIS 6401) belonging to an ordinary tire having an extra tread, parts being shown vertical center section through the rotational axis of the tire.
  • the tire shown in FIG. 7 has a size of 24.00-49 42PR, 42 PR being indicated on the basis of a cotton yarn.
  • the tire shown in FIG. 7 comprises a bead member 1 composed of three sets of bead cores 1a, 1b, 1c and a carcass ply 2 composed of 32 plies each formed of a nylon cord of 1,260 denier/2 strands.
  • Ten plies 2a of the total 32 plies are wound about the bead core 1a from the inside toward the outside thereof and secured to the bead member 1.
  • Ten plies 2b are wound about the bead core 1b from the inside toward the outside thereof and secured to the bead member 1. Those four plies 3 of the plies 2b which are located outside thereof at a crown center portion of the tire are skipped by a width which is substantially the same as the width of two breaker layers 7a, 7b each having an excellent cut resistant property. As a result, the number of plies 2b at the crown center portion of the tire protected by the steel breakers 7a, 7b becomes 6, but the ten plies 2b are extended from the hump portion of the tire to the bead core 1b and are wound about the bead core 1b from the inside toward the outside thereof and secured to the bead member 1 to constitute a side reinforcing ply.
  • plies 4 which are extended from the crown center portion of the tire through the side portion thereof to a position located above the bead core 1b.
  • plies 4 may be designated a cap ply.
  • the number of plies 2b at the crown center portion of the tire protected by the steel breakers 7a, 7b becomes 6, but the 10 plies 2b are extended from the hump portion of the tire to the bead core 1b and would about the bead core 1b from the inside toward the outside thereof and secured to the bead member 1.
  • Ten plies 2c are wound about the bead core 1c from the inside toward the outside thereof and secured to the bead member 1. Those four plies 3' of the plies 2c which are located outside thereof at the crown center portion of the tire are skipped in the same manner as in the case of the plies 2b.
  • the number of plies 2c at the crown center portion of the tire protected by the steel breakers 7a, 7b becomes 6, but the ten plies 2c are extended from the hump portion of the tire to the bead core 1c and are wound about the bead core 1c from the inside toward the outside thereof and secured to the bad member 1 to constitute a side reinforcing ply.
  • two outermost plies 2d are extended from the crown center portion of the tire to the bead member 1 where these two outermost plies 2d are extended from the outside along the lower surface of the bead cores 1c, 1b, 1a toward the inside thereof and secured at their inner ends to a toe portion 1d of the bead member 1.
  • the above mentioned combination of the crown center skipped carcass ply construction and the cap ply makes it possible to reduce the thickness of the crown center portion of the tire by approximately 10 mm if compared with the thickness of the crown center portion of a tire whose carcass ply is composed of 32 plies.
  • the other construction is substantially the same as that of the example 4.
  • the safety factor of the carcass ply of the tire of the example 5 according to the invention obtained by the above mentioned calculation formulae was 13.2. It is a matter of course that the eight plies in total for reinforcing the side portion only of the tire are not taken into the calculation.
  • FIG. 8 is shown a modified embodiment of the tire according to the invention.
  • the breaker layers 7a, 7b are divided into a plurality of sections in their widthwise direction, respectively, the sections being spaced apart from each other.
  • FIG. 9 is shown another modified embodiment of the tire according to the invention.
  • one protective layer 8 composed of a rubberized fabric containing organic fiber cords and superimposed about the breaker layers 7a, 7b.
  • FIG. 10 is shown a further modified embodiment of the tire according to the invention.
  • a pair of protective layers 8', 8' are superimposed about side edges only of one breaker layer 7, respectively.
  • Those protective layers 8, 8' serves to improve recap property of the tire.
  • FIG. 11 is shown a still further modified embodiment of the tire according to the invention.
  • one protective layer 8" is extended from the crown center portion of the tire through the side portions and arrives at a position located near the bead members.
  • FIG. 12 is shown another modified embodiment of the tire according to the invention.
  • the above mentioned protective layers 8, 8', 8", 8a, 8b are not taken into the calculation of the safety factor.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Tires In General (AREA)
  • Detergent Compositions (AREA)
US05/664,227 1975-03-15 1976-03-05 Pneumatic tire for off-road vehicles Expired - Lifetime US4043372A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JA50-31579 1975-03-15
JP50031579A JPS51106906A (en) 1975-03-15 1975-03-15 Kotaikyusei jufuka arechisokoyokukiiritaiya

Publications (1)

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US4043372A true US4043372A (en) 1977-08-23

Family

ID=12335082

Family Applications (1)

Application Number Title Priority Date Filing Date
US05/664,227 Expired - Lifetime US4043372A (en) 1975-03-15 1976-03-05 Pneumatic tire for off-road vehicles

Country Status (12)

Country Link
US (1) US4043372A (fr)
JP (1) JPS51106906A (fr)
BR (1) BR7601557A (fr)
CA (1) CA1028605A (fr)
DE (1) DE2610714A1 (fr)
ES (1) ES445988A1 (fr)
FR (1) FR2304489A1 (fr)
GB (1) GB1541238A (fr)
LU (1) LU74556A1 (fr)
NO (1) NO143787C (fr)
SE (1) SE7603030L (fr)
ZA (1) ZA761408B (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4142568A (en) * 1977-02-23 1979-03-06 The Goodyear Tire & Rubber Company Bias tire with embedded wire breakers
US4651448A (en) * 1984-12-19 1987-03-24 Contax Sports, Inc. Golf spike assembly
US6189586B1 (en) 1998-10-15 2001-02-20 Warren L. Guidry Pneumatic rubber tire for on/off-road vehicles
US20090178750A1 (en) * 2008-01-15 2009-07-16 Maurice Taylor Multiple bead radial tire

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2702770B2 (ja) * 1989-04-11 1998-01-26 住友ゴム工業株式会社 空気入りタイヤ
JP2688522B2 (ja) * 1989-05-24 1997-12-10 住友ゴム工業株式会社 空気入りタイヤ
US5509455A (en) * 1994-04-12 1996-04-23 The Goodyear Tire & Rubber Company Aircraft tire including reinforcement inserts
JP5440320B2 (ja) * 2010-03-29 2014-03-12 横浜ゴム株式会社 重荷重用空気入りバイアスタイヤ

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB815139A (en) * 1956-05-23 1959-06-17 Gen Tire & Rubber Co Aircraft tyre
US3050098A (en) * 1961-06-28 1962-08-21 Goodyear Tire & Rubber Tire with sidewall inserts
US3442315A (en) * 1965-06-01 1969-05-06 Pneu Englebert Soc Franc Pneumatic tires
US3568750A (en) * 1967-06-13 1971-03-09 Continental Gummi Werke Ag Pneumatic vehicle tire
US3703203A (en) * 1970-06-12 1972-11-21 Goodyear Tire & Rubber Radial wire tire having improved sidewall cut resistance
US3982580A (en) * 1973-10-23 1976-09-28 Bridgestone Tire Company Limited Pneumatic tire for construction vehicles

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5632123B2 (fr) * 1973-01-18 1981-07-25

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB815139A (en) * 1956-05-23 1959-06-17 Gen Tire & Rubber Co Aircraft tyre
US3050098A (en) * 1961-06-28 1962-08-21 Goodyear Tire & Rubber Tire with sidewall inserts
US3442315A (en) * 1965-06-01 1969-05-06 Pneu Englebert Soc Franc Pneumatic tires
US3568750A (en) * 1967-06-13 1971-03-09 Continental Gummi Werke Ag Pneumatic vehicle tire
US3703203A (en) * 1970-06-12 1972-11-21 Goodyear Tire & Rubber Radial wire tire having improved sidewall cut resistance
US3982580A (en) * 1973-10-23 1976-09-28 Bridgestone Tire Company Limited Pneumatic tire for construction vehicles

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4142568A (en) * 1977-02-23 1979-03-06 The Goodyear Tire & Rubber Company Bias tire with embedded wire breakers
US4651448A (en) * 1984-12-19 1987-03-24 Contax Sports, Inc. Golf spike assembly
US6189586B1 (en) 1998-10-15 2001-02-20 Warren L. Guidry Pneumatic rubber tire for on/off-road vehicles
US20090178750A1 (en) * 2008-01-15 2009-07-16 Maurice Taylor Multiple bead radial tire

Also Published As

Publication number Publication date
NO760706L (fr) 1976-09-16
NO143787B (no) 1981-01-05
JPS51106906A (en) 1976-09-22
CA1028605A (fr) 1978-03-28
AU1160976A (en) 1977-05-26
SE7603030L (sv) 1976-09-16
LU74556A1 (fr) 1976-09-01
GB1541238A (en) 1979-02-28
BR7601557A (pt) 1976-09-14
ZA761408B (en) 1977-02-23
JPS577924B2 (fr) 1982-02-13
FR2304489A1 (fr) 1976-10-15
DE2610714A1 (de) 1976-09-16
ES445988A1 (es) 1977-06-16
NO143787C (no) 1981-04-15
FR2304489B1 (fr) 1978-07-07

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